Hardline President Mahmoud Ahmadinejad won re-election by a thumping margin, official figures showed Saturday, but his moderate challenger rejected the tally as a dangerous charade that could lead to tyranny.
The scale of Ahmadinejad's victory -- he took nearly twice as many votes as former Prime Minister Mirhossein Mousavi with counting almost complete after Friday's poll -- upset widespread expectations that the race would at least go to a second round.
Interior Minister Sadeq Mahsouli said Ahmadinejad won 62.6 percent of the vote and Mousavi 33.75 percent. Turnout was a record 85 percent of eligible voters.
Mousavi protested against what he said were many obvious violations.
I'm warning I will not surrender to this dangerous charade. The result of such performance by some officials will jeopardize the pillars of the Islamic Republic and will establish tyranny, Mousavi said in a statement made available to Reuters.
He had been due to hold a news conference, but police at the building turned journalists away, saying it was canceled.
Iranian and Western analysts abroad greeted the results with disbelief. They said Ahmadinejad's re-election would disappoint Western powers aiming to convince Iran to halt work they suspect is aimed at making bombs, and could further complicate efforts by U.S. President Barack Obama to reach out to Tehran.
It doesn't augur well for an early and peaceful settlement of the nuclear dispute, said Mark Fitzpatrick at London's International Institute for Strategic Studies.
A bitterly fought campaign generated strong interest around the world and intense excitement inside Iran. It revealed deep divisions among establishment figures between those backing Ahmadinejad and those pushing for social and political change.
Ahmadinejad accused his rivals of undermining the Islamic Republic by advocating detente with the West. Mousavi said the president's extremist foreign policy had humiliated Iranians.
Friday night, before official results emerged, Mousavi had claimed to be the definite winner. He said many people had been unable to vote and ballot papers were lacking.
He also accused authorities of blocking text messaging, with which his campaign tried to reach young, urban voters.
State election commission figures showed Ahmadinejad had secured a second four-year term with 61.6 percent of ballots against 32.5 percent for Mousavi with 39 million votes counted. It put the turnout at 80 percent of 46 million eligible voters.
Trita Parsi, president of the Washington-based National Iranian American Council, expressed disbelief at the wide margin in Ahmadinejad's favor. It is difficult to feel comfortable that this occurred without any cheating, Parsi said.
Ali Ansari, who heads the Institute for Iranian Studies at St Andrews University in Scotland, said: People will wake up today in Iran in shock, not that Ahmadinejad has won, but that he has won on such a dramatic scale.
Western capitals had hoped a victory for Mousavi could help ease tensions with the West, which is concerned about Tehran's nuclear plans, and improve chances of engagement with Obama, who has talked of a new start if Tehran unclenches its fist.
Now they must again deal with Ahmadinejad, who has refused talks with six world powers over Iran's nuclear program.
The three-week election campaign was marked by mudslinging, with Ahmadinejad accusing his rivals of corruption. They said he was lying about the economy. Inflation, officially put at 15 percent, and unemployment were core issues in the debate.
It was unclear how Mousavi's supporters, who thronged the streets of Tehran nightly during the campaign, might react to Ahmadinejad's victory. U.S. strategic intelligence group Stratfor called the situation potentially explosive.
Scuffles broke out overnight between police and chanting Mousavi supporters in a Tehran square, a Reuters witness said. Police said they had boosted security across the capital. All gatherings have been banned until final results are declared.
Ahmadinejad draws his bedrock support from rural areas and poorer big city neighborhoods. Mousavi enjoys strong backing in wealthier urban centers, especially among women and the young.
Two other candidates attracted only tiny voter support.
Ahmadinejad, 52, won power four years ago, vowing to revive the values of the 1979 Islamic revolution. He has expanded the nuclear program, which Iran says is only for electricity generation, and stirred international outrage by denying the Holocaust and calling for Israel to be wiped off the map.
If there was a shadow of hope for a change in Iran, the renewed choice of Ahmadinejad expresses more than anything the growing Iranian threat, Israel's Deputy Foreign Minister Danny Ayalon said in a statement. The international community must stop a nuclear Iran and Iranian terror immediately.
Ahmadinejad, who has cultivated relations with U.S. foes around the world, received telephoned congratulations from Venezuelan President Hugo Chavez, the Fars news agency said.
Mousavi, 67, rejects Western demands that Iran halt uranium enrichment, but argued for a different approach to Iran-U.S. ties and nuclear talks -- although these are policy areas ultimately controlled by Supreme Leader Ayatollah Ali Khamenei.
The United States has had no ties with Iran, the world's fifth biggest oil exporter, since shortly after the 1979 Islamic revolution. Obama said his country had tried to send a clear message that we think there is the possibility of change.
(Additional reporting by Hossein Jaseb, Hashem Kalantari, Zahra Hosseinian in Tehran and Alistair Lyon in Beirut; Writing by Dominic Evans and Fredrik Dahl; Editing by Alistair Lyon)